 Winter is coming. As temperatures begin to drop, it's important for chemical and process facilities to be prepared for the unique safety challenges posed by cold weather. The Chemical Safety Board has conducted several investigations where ineffective winterization practices and programs contributed to a major chemical incident. The POM facility in La Porte, Texas, outside of Houston. Our investigation found that days prior to the incident, water had mixed with liquid methylmer captain and piping. Due to cold weather in the Houston area, this mixture formed a solid material called a hydrate, which blocked the piping. Operations personnel in one area of the plant attempted to clear the blockage. And later, in a separate area of the plant, two workers opened valves in response to what they believed was a routine unrelated pressure problem. But the CSB discovered that the high pressure in that other piping was due to the fact that liquid methylmer captain was once again flowing through the original, now unblocked pipes. Nearly 24,000 pounds of deadly methylmer captain escaped through the open valves in a poorly ventilated manufacturing building. One of those workers made a distress call, and two additional workers died responding to that call. The CSB found that lack of winterization procedures also contributed to a massive fire that took place in 2007 at the Valero Refinery near Sunray in the Texas Panhandle. The fire occurred in a unit that used large amounts of high pressure liquid propane. Years earlier, the unit had been reconfigured, creating a dead leg, or a section of piping without any flow of liquid. Dead legs are particularly vulnerable to the hazards of freezing, and the dead leg at Valero was blocked on one side by a leaky valve. Water, which were contained in the liquid propane, sang past the leaking valve. The temperature fell to 6 degrees Fahrenheit. The water froze, expanded, and cracked the pipe. The following day, as the weather warmed, the ice melted, and propane began jetting from the broken pipe and ignited. The fire seriously burned three people, shut down the refinery for two months. These two serious accidents illustrate the importance of establishing effective winterization programs at refineries, chemical plants, and other facilities that handle hazardous materials. The CSB has established key winterization safety lessons that facilities should follow. Facilities should effectively identify and address the risk of freeze-related hazards to piping and process equipment through process hazard analyses, management of change evaluations, pre-startup safety reviews, and operating procedures. Create and implement a winterization checklist to ensure that their plant and process systems are ready for cold weather. Establish a formal written freeze protection program. Survey piping systems for dead legs and ensure they are properly isolated, removed, or winterized. And systematically review process units, including infrequently used piping and equipment to identify and mitigate freezing hazards.